Elenco Fiber Optics Voice Data Kit - Manual (Page 19)

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To achieve high-quality images, very small fibers are required
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In the previous experiments you will have noticed that the images through the different fiber
optic imaging elements appeared different. Two items determine how an image appears through a fiber
bundle — resolution and transmission. Resolution is determined by how small the fiber diameters are.
See for yourself.
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Ulexite (off-white, irregular-shaped rock)
2.5 cm (1 inch) long fiber bundle (constructed in Experiment 11)
10
Ч 10 Ч 2.5 mm (.4 Ч .4 Ч .1 inch) fiber optic faceplate
3 mm diameter × 4.3 cm (1/8 × 1-3/4 inch) image conduit (glass-like rod)
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• Place the Ulexite, fiber bundle, faceplate and image conduit over one column of letters shown at
the right.
• Slowly move all the items down each letter, moving
from larger to smaller letters.
• Determine which of the fiber optic elements produces
the best image (highest resolution) of the smaller
letters.
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You should have found that the fiber optic faceplate
produces the clearest images with the small letters. The 3
cm (1/8 inch) diameter image conduit has less resolution
than the faceplate, but more than the Ulexite. The Ulexite
image also is yellowish and has cloudy or dark spots in it.
The 2.5 cm long bundle that you constructed in a previous
experiment would have the poorest resolution of all tested items.
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The image quality transmitted by each of the bundles is directly related to the size of fiber from
which it is made. Smaller diameter equals better resolution. The fiber optic faceplate, made with fibers
10
µm (.0004 inch) in diameter, has the highest resolution. The 3 mm diameter image conduit has 50
µm diameter fibers and is the next best. The Ulexite does not have actual fibers, but rather small
crystals that vary in cross-section. We can not specify a dimension, but estimate them to be slightly
larger than the 50
µm diameter found in the 5 cm length of image conduit. The image through the
Ulexite has a yellowish cast due to the sodium in it. The poorest resolution is found with the fiber
bundle you constructed in Experiment 11 using the .5 mm fibers.
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Randomly arranged fibers can be bundled together like spaghetti, but imaging bundles take
considerably more care. They are made in a series of
phases. First a fiber is selected that is about 2.5 mm (.1
inch) in diameter. A group of these fibers is bundled
together, heated and shrunk into rigid "multifiber" bundles
about 2 mm (.08 inch) in diameter. Then several
multifibers bundles are packed together, heated and shrunk
to produce a rigid bundle containing thousands of fibers.
The individual fibers can vary from 3 to 20
µm in diameter.
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